This problem is generally caused by the abnormality of pan detection circuit, but it does not rule out the abnormality of driving circuit.

1, check the thermistor for short circuit or open circuit.

2. Check whether the high-power resistor is damaged or aging.

3. Check whether the filter capacitor, resonant capacitor and IGBT are damaged.

4. Check whether the four-voltage comparator LM339 is damaged.

5. Check whether the transistor driver tubes of S8050 and S8850 are damaged.